[Bug tree-optimization/27109] Simplify "a - 10 > 150" into "a > 160" when range of a is known (in VRP or somewhere else)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27109 Andrew Pinski changed: What|Removed |Added Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot gnu.org --- Comment #7 from Andrew Pinski --- I suspect we could add it to simplify_compare_using_ranges_1 very easy. Let me look into that.
[Bug tree-optimization/27109] Simplify "a - 10 > 150" into "a > 160" when range of a is known (in VRP or somewhere else)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27109
--- Comment #6 from Andrew Pinski ---
Another testcase which shows up via the autovectorizer aliasing checks
int g(unsigned int a)
{
if (a == 0) __builtin_unreachable();
unsigned int t = a;
a += -1;
return a > 3u;
}
[Bug tree-optimization/27109] Simplify "a - 10 > 150" into "a > 160" when range of a is known (in VRP or somewhere else)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27109 --- Comment #5 from Andrew Pinski --- *** Bug 101815 has been marked as a duplicate of this bug. ***
[Bug tree-optimization/27109] Simplify "a - 10 > 150" into "a > 160" when range of a is known (in VRP or somewhere else)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27109 Andrew Macleod changed: What|Removed |Added CC||amacleod at redhat dot com --- Comment #4 from Andrew Macleod --- well, in evrp we now produce: === BB 6 Imports: a_3(D) Exports: _1 a_3(D) _1 : a_3(D)(I) a_3(D) unsigned int [100, 200] : _1 = a_3(D) + 4294967286; if (_1 > 150) goto ; [INV] else goto ; [INV] _1 : unsigned int [90, 190] 6->7 (T) _1 : unsigned int [151, 190] 6->7 (T) a_3(D) : unsigned int [161, 200] 6->8 (F) _1 : unsigned int [90, 150] 6->8 (F) a_3(D) : unsigned int [100, 160] we know its not going to overflow. who or what should make the decision? looks like some sort of simplification or peephole. Also note that you can now find this out from any pass with the range_query infrastructure that Aldy added: at the start of the pass call enable_ranger() for context sensitive info, and then anywhere you can get_range_query()->range_of_expr (r, stmt, name) will get a range. so for the initial stmt 1 = a_3(D) + 4294967286; asking for the range of a_3 on this stmt would give you [100,200] or asking for the range of the stmt (or i_1 in the next statetment) will give you [90,190] Aldy has also implemented an overflow checker for expressions.. not sure it applies to stmts.. yet. If any of this interests you, send him a note. We're still working out user case functionality, so if there is anything else we need to present this kind of info, let us know. I think he's planning to write a guide for this next week. Another option is to work it backwards. given the stmt: # RANGE [90, 190] NONZERO 255 _1 = a_3(D) + 4294967286; range-ops can tell you that if _1 is [90,190] then it can evaluate the expression and solve that a_3 is [100,200].. if that helps. internally it knows if there was a potential overflow, but that isnt exported in any useful way way at the moment.
[Bug tree-optimization/27109] Simplify "a - 10 > 150" into "a > 160" when range of a is known (in VRP or somewhere else)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=27109
Andrew Pinski changed:
What|Removed |Added
Last reconfirmed|2007-07-01 00:53:44 |2021-6-2
--- Comment #3 from Andrew Pinski ---
Here is a better testcase:
void bar(void);
void goo(void);
void
foo (unsigned a)
{
if (a < 100)
return;
goo();
if (200 < a)
return;
if (a - 10 > 150)
bar ();
}
Note the original testcase is optimized correctly in reassoc1 but that was not
the point of it.
Anyways we have:
# RANGE [90, 190] NONZERO 255
_1 = a_3(D) + 4294967286;
if (_1 > 150)
4294967286 is -10
[Bug tree-optimization/27109] Simplify a - 10 150 into a 160 when range of a is known (in VRP or somewhere else)
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27109 --- Comment #2 from Marc Glisse glisse at gcc dot gnu.org 2012-12-04 18:48:27 UTC --- This seems to be well handled in reassoc1 now: Optimizing range tests a_2(D) -[0, 99] and +[0, 200] and -[10, 160] into a_2(D) + 4294967135 = 39
[Bug tree-optimization/27109] Simplify a - 10 150 into a 160 when range of a is known (in VRP or somewhere else)
--- Comment #1 from rguenth at gcc dot gnu dot org 2006-12-28 12:03 --- Confirmed. compare_values needs to be teached to look at value ranges for operands and decide on overflow there - but only for substitute and fold as earlier we can have invalid intermediate value ranges. -- rguenth at gcc dot gnu dot org changed: What|Removed |Added CC||rguenth at gcc dot gnu dot ||org Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Last reconfirmed|-00-00 00:00:00 |2006-12-28 12:03:15 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27109
[Bug tree-optimization/27109] Simplify a - 10 150 into a 160 when range of a is known (in VRP or somewhere else)
-- pinskia at gcc dot gnu dot org changed: What|Removed |Added Severity|normal |enhancement http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27109
